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From: "Alec Matusis" <matusis@yahoo.com>
To: <dev@httpd.apache.org>
References: <543025.74626.qm@web81108.mail.mud.yahoo.com>
 <4700AE6C.3070802@apache.org>
In-Reply-To: <4700AE6C.3070802@apache.org>
Subject: RE: 2.0.54 unstable, requests time-out, NO warnings in logs
Date: Mon, 1 Oct 2007 16:04:42 -0700
Message-ID: <00f901c8047f$73e42b70$5bac8250$@com>
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> Have you checked without the MaxMemFree setting?
> Why do you use MaxMemFree with such a small value at all?

I finally removed MaxMemFree altogether, and it crashed again. Nothing =
in
the apache error logs, but this is how /server-status looks like during =
the
crash:

300 requests currently being processed, 0 idle workers=20
WCRRRRRRCRRRRRRRRCCRRRRRRRRRRRRRRRCCRWWRRRCRWRRCRRCRWRRWRRRRRRRC
RRCRRRRCRCRRWRRRRWWCRRRWRRRWRCRRRCRRRRRRRRRCRRCRRRCCCRRCRRRRCCWR
RCRRRRRRRRRRRRRRRRWWRRRWRWRWCCCWWWRCRRRRRCRCCWRRWRCRCRWRRRRCRRRR
RRRRWRRRWRRRCRRCRRCRRRCRRRRRRRRRRRRRRRRCCCRWRRRRRRRRRRRRCRRRCRRR
RRCRRRRRRRRCRWCRCRRRRRRRWWCWRRCWRRRCRRCRRRCR

Immediately after I restarted the apache after the crash, I did get

[Mon Oct 01 15:20:49 2007] [notice] mod_python: Creating 32 session =
mutexes
based on 300 max processes and 0 max threads.
[Mon Oct 01 15:20:49 2007] [notice] Apache/2.0.54 (Unix) =
mod_python/3.1.4
Python/2.4.1 configured -- resuming normal operations
****[Mon Oct 01 15:21:25 2007] [error] server reached MaxClients =
setting,
consider raising the MaxClients setting***

but it's strange that this message was not written before or during the
crash, even though /server-status shows no available free child =
processes.


> -----Original Message-----
> From: Ruediger Pluem [mailto:rpluem@apache.org]
> Sent: Monday, October 01, 2007 1:23 AM
> To: dev@httpd.apache.org
> Subject: Re: 2.0.54 unstable, requests time-out, NO warnings in logs
>=20
>=20
>=20
> On 10/01/2007 08:32 AM, Alec Matusis wrote:
> > We are running a busy Apache/2.0.54 server on 2.6.9 kernel, that
> suddenly becomes very slow- requests either time out, or it takes 10-
> 20sec to serve a 1K thumbnail.
> > It is somewhat correlated with load spikes, but not perfectly (by
> looking at the bandwidth graph, it never happens during the low
> bandwidth periods at night, but it does not coincide with peaks of =
b/w)
> >
> > When we initially encountered an apache overload, it was always
> accompanied with
> >
> > [error] server reached MaxClients setting, consider raising the
> MaxClients setting
> >
> > in the apache error log. We also got
> >
> > kernel: possible SYN flooding on port 80. Sending cookies.
> >
> > in /var/log/messages system log.
> >
> > After that I raised MaxClients from 200 to 300. The problem =
initially
> disappeared, but after our bandwidth grew a bit more, we got this
> behavior again.
> > Now apache crashes (becomes very slow) silently, with no warning in
> apache error logs at all (although we still get SYN flood message in
> the system log)
> > When apache is this 'slow' regime, /server-status still shows
> available slots, i.e. MaxClients is not reached.
> >
> > This is the relevant part of httpd.conf:
> >
> > ServerLimit 300
> > # we are using prefork MPM
> > StartServers 10
> > MinSpareServers 5
> > MaxSpareServers 20
> > MaxClients 300
> > MaxRequestsPerChild 10000
> > MaxMemFree 2500
> >
> > The server has 4GB of physical RAM and 4GB of swap. During these
> apache =93slowdowns", the swap size is still 0 and vmstat shows no
> swapping at all.
> > I suspect the problem may be in
> >
> > MaxMemFree 2500
>=20
> Have you checked without the MaxMemFree setting?
> Why do you use MaxMemFree with such a small value at all?
>=20
> Regards
>=20
> R=FCdiger